Allow turning global privs on/off

[ylt]

Allow global privileges (maybe multiple) to be assigned to a user (i.e. admin, developer, etc). User can then choose if that role is visible/active.

By default, no role should be selected and staff should have to elevate themselves to that level as needed.

This allows site staff to be regular members within a community and to be promoted within it normally, without having concerns of overstepping. Promoted staff should be much more comfortable using their powers if they've been given them by the room owner. While also having the means to grant themselves higher perms (global) if necessary.

Users without their global perms enabled should still be highlighted.